This invention relates generally to aircraft surveillance systems, and more particularly to secure aircraft surveillance systems that are configured for alerting air traffic controllers if an aircraft departs substantially from an expected flight path or pattern of behavior.
The terrorist hijacking and suicide crashes of four U.S. civilian airliners on Sep. 11, 2001, were tragic and unforeseen. The inability of the air traffic control and civil defense infrastructure to respond effectively to the situation as it developed was due, in part, to limitations of the current radar-based surveillance infrastructure.
Because of timing delays and accuracy limitations inherent in the design of current radar-based air traffic control systems, controllers are unable to determine the real-time intent of aircraft they are tracking. Moreover, current radar surveillance systems depend on transponder responses from the aircraft to operate at maximum efficiency. The September 11 terrorists disabled or turned off some aircraft transponders in the cockpit of the hijacked aircraft, making it difficult to track the aircraft. This, combined with the limitations of current surveillance radar systems, made it nearly impossible for controllers to realize that three of the aircraft had turned into collision courses with ground targets.
Thus, there is a need for an aircraft surveillance system that cannot be interrupted by unauthorized persons. There is a further need for an improved surveillance system that is configured to warn ground controllers when an aircraft acts outside of cleared parameters. Furthermore, there is a need for systems that alert ground controllers if someone in the aircraft is attempting to send a false signal to deceive the controllers into believing that the aircraft is following a planned course when in fact it has been diverted. In addition, there is a need for an improved surveillance system that allows pilots to quickly and reliably issue a distress signal upon realizing that their aircraft is in danger of being hijacked.
The present invention meets the objectives set forth above by providing an on-board broadcast surveillance system and method that cannot be interrupted and that provides three-dimensional position information to ground or airborne controllers via a data transmitter. Optionally, the broadcast information may include the Ownship aircraft""s aircraft ID and intended path. Other optional components according to the invention include a system and method for validating messages received from the aircraft, and an alternative system and method for determining the aircraft""s position if a primary navigation aid, such as the Global Positioning System (xe2x80x9cGPSxe2x80x9d), is not available.
In a preferred embodiment, the invention equips an aircraft with a small uninterruptible Universal Access Transceiver/Automatic Dependent Surveillancexe2x80x94Broadcast (xe2x80x9cUAT/ADS-Bxe2x80x9d) transmitter (or other suitable transmitter) that is capable of broadcasting aircraft ID, three-dimensional position and aircraft intent. The device contains an internal GPS receiver to determine aircraft position and has an uninterruptible power supply that can not be disabled from the cockpit. The device, which is preferably located in the aircraft""s equipment bay, automatically begins broadcasting aircraft position, ID and intent the moment the aircraft is powered up and continues to broadcast that information, in real-time, until the aircraft is on the ground and shut down. Via an optional external interface, the device may receive and broadcast flight plan information from the on-board flight management computer. Such information is then made available for comparison to originally filed ATC flight plan data. This allows air traffic control (xe2x80x9cATCxe2x80x9d) authorities to detect any inappropriate changes to the aircraft""s intended destination shortly after the changes are entered into the aircraft""s flight management computer.
The invention may further provide a ground infrastructure that preferably comprises a plurality of receivers for receiving the information transmitted from the aircraft. Preferably, about 600 low-cost UAT ADS-B receivers would be located throughout the continental United States to provide full CONUS real-time surveillance. The system would be equipped with the capability of determining whether the equipped aircraft were flying within the xe2x80x9cnormalxe2x80x9d parameters of its flight plan. Upon detecting a deviation from the flight plan, the system would provide controllers and civil defense authorities with an immediate alert. If an aircraft deviated from its flight plan, its ADS-B signal would continue to provide real-time position, altitude, heading and intent of the aircraft to air traffic control and civil defense authorities. Airborne controller stations may optionally replace some or all ground controller stations.
A system and method for validating messages received from the aircraft may be based on the ability of the UAT to perform range measurements based on signal propagation time, giving rise to several advantages. More specifically, the system can determine whether the aircraft""s reported position (i.e., the position transmitted by the aircraft) is valid by comparing a range that corresponds to the target""s reported position with a range derived from signal propagation times. As an additional validity check, or if GPS service is unavailable, the position of a particular aircraft can be determined by receiving at least a partial State Vector (identity plus altitude) at multiple controller stations, and then using time of reception differentials among a network of such stations to compute lines of position.
Additional anti-spoofing can be accomplished by validating the last received position information with a dead reckoning algorithm. When implementing this functionality, any jumps in speed and velocity outside a preset limit are rejected.
In the event that GPS position information becomes unavailable, a dead reckoning function can be used to estimate the aircraft""s position. Inexpensive inputs such as heading from a magnetic flux gate, changes in velocity from a solid state accelerometer, and altitude from an optional self-contained barometer can also be used to enhance the dead reckoning calculation. As will be understood by one skilled in the art, this self-contained barometer is optional because the aircraft is preferably equipped with an altimeter that is not affected by any loss of GPS position information.
The invention may further include a panic button within the cockpit of the aircraft that, when activated, transmits a signal to an aircraft information broadcasting system indicating that the Ownship aircraft is in danger of being hijacked. The aircraft information broadcasting system then immediately transmits a signal that triggers an appropriate alarm at a ground station. This aspect of the system is advantageous because it allows pilots to issue a distress signal without having to enter a complex code. Also, in a preferred embodiment of the invention, the aircraft information broadcasting system is preferably tamper-proof and located outside the aircraft""s cockpit. As a result, it is unlikely that a hijacker would be able to disable the aircraft information broadcasting system before the pilot transmits a distress signal to air traffic control.
More particularly, a system according to a preferred embodiment of the invention comprises a housing defining an interior portion and an aircraft information broadcasting system that is disposed within the interior portion of the housing. In this embodiment of the invention, the system is configured for broadcasting flight-related information that is related to the Ownship aircraft""s current flight. The housing is configured for restricting access to the aircraft information broadcasting system while the aircraft is in flight.
In one embodiment of the invention, the system is configured for broadcasting the flight-related information in real time and in a substantially continuous manner while the aircraft is in flight. In a particular embodiment of the invention, the flight-related information includes one or more of the following: (1) the aircraft""s current flight ID, (2) the current three-dimensional position of the aircraft, (3) the aircraft""s current velocity, (4) waypoint information for the aircraft; and (5) the aircraft""s current intent information.
In another embodiment of the invention, the system""s housing comprises a robust material that substantially surrounds the aircraft information broadcasting system and that thereby restricts access to the aircraft information broadcasting system. In a particular embodiment of the invention, this housing is configured to be locked while the aircraft is in flight. In one embodiment of the invention, the housing and the aircraft information broadcasting system are configured for being disposed within a portion of the aircraft that is outside of the aircraft""s cockpit while the aircraft is in flight. The aircraft information broadcasting system is preferably located within the aircraft""s equipment bay.
In yet another embodiment of the invention, the system comprises an information reception and analysis station that is configured for comparing intent information that is broadcast from the aircraft""s aircraft information broadcasting system with approved flight path information to determine whether the aircraft is being directed toward an improper destination. In this embodiment of the invention, the system is preferably configured for generating an alarm if the intent information differs from the approved flight path information by more than a predetermined amount.
In a further embodiment of the invention, the system comprises an information reception and analysis station that is configured to validate information received from the aircraft information broadcasting system using triangulation techniques. Similarly, the system is preferably configured for generating an alarm if one or more measured aspects of the aircraft""s current flight differs from the expected or measured flight characteristics of the aircraft.
An additional embodiment of the invention comprises a method of broadcasting information related to an aircraft. This method comprises the steps of: (1) providing a housing that defines an interior portion and that is configured for restricting access to the housing""s interior portion while the aircraft is in flight; (2) providing an aircraft information broadcasting system that is configured for broadcasting flight-related information from the aircraft; (3) positioning the aircraft information broadcasting system within the interior portion of the housing; and (4) using the aircraft information broadcasting system to broadcast the flight-related information from the aircraft while the aircraft information broadcasting system is disposed within the interior portion of the housing and while the housing is restricting access to the interior portion.
Yet another embodiment of the invention comprises a method of tracking an aircraft. This method comprises the step of providing an aircraft with an information broadcasting system that is configured for broadcasting information related to a current flight of the aircraft in a substantially uninterruptible manner while the aircraft is in flight.
The invention described above is expressed in terms of systems and methods that are configured for executing, or that include, various steps. However, it will be understood by one skilled in the art that the invention also includes systems that are configured to perform, and computer-readable media that include computer-executable instructions for executing, the steps included within the above-described methods. Similarly, one skilled in the art will understand that the invention also includes methods that include, and computer-readable media that include computer-executable instructions for executing, the steps executed by the above-described systems.